In conventional cellular networks, a device connected through a radio access channel has often been thought of as a mobile device. As a result, the rules governing the behavior of the device, and the manner in which the device is handled in the network have been designed to account for the fact that the device is mobile and will be prone to moving between cells.
This perception is starting to change, as there is a growing demand for Machine-to-Machine (M2M) devices, which engage in what is often referred to as of machine type device communication (MTC).
The machine type device is often viewed as a sensor or a meter, such as an electrical or water consumption meter, although other types of connected devices are known. These devices use radio access channels to connect to the same data network that mobile devices connect to, but they are often less mobile and more tolerant of many other conditions. As these devices become more common, the expected number of deployed MTC devices will increase, possibly into the millions. As the numbers of deployed devices expand, the number of active devices in a network cell will also likely increase. One skilled in the art will appreciate that there are practical limits to the number of different devices that can share a cell in a radio access network. Beyond that limit, the quality of connection is degraded, and network planning must be re-evaluated. A number of different approaches can be pursued to mitigate the effects of a large number of MTC devices in a cell. One solution is to restrict the number of MTC devices will a connection to the cellular network through the use of other networking technologies. As an example, devices can be connected to each other through a WiFi network (IEEE 802.11x) and only one of the devices will then connect to the radio access network. This offers a number of benefits, but can introduce problems in allowing a plurality of different vendors from offering solutions.
Even with the use of gateways, the number of devices in a given network cell can increase to the point at which there are too many MTC devices active at a single time. When this happens, the degraded radio access network connection will be noticeable, will adversely affect the experience of human operated devices and will cause operational difficulties for the network. Often the communications of an MTC device are not immediately time-sensitive, and can easily be delayed when data traffic volumes are high, whereas for a human operated device, this is seen by the user as being a network outage. As the number of MTC devices increases, there is an increased likelihood of the MTC devices contributing to or causing network overloading. This will likely be caused if too many machine type devices communicate with the network at the same time. Even if each MTC device only generates a small amount of data signaling traffic, a sufficiently large volume of devices will lead to network overloading.
From the perspective of a network operator it is desirable to reduce the amount of network signaling caused by these devices. It may also be advantageous for the MTC device to remain offline if it is not active. However, the devices often cannot be inactivated as they must be reachable by network elements. Conventional devices can enter a sleep mode to conserve power (which is very useful when the device is powered by batteries) but the device typically remains sufficiently active to respond to a network page. To the network, this device is still attached, and consumes resources in the network. From the network perspective, the device is either seen as being attached to the network or detached from the network. When a device is connected, or attached to the network, resources are consumed in the network to allow the device to be contacted. When the device is detached, the network no longer has enough information to contact the device.
Many mobile network standards are developed by the 3rd Generation Partnership Project (3GPP). Current 3GPP standards define devices (also referred to as user equipment (UE)) as being either REGISTERED or DEREGISTERED. A REGISTERED device can be IDLE or connected. In the DEREGISTERED state, no UE context information is saved in the network. The UE location (part of the context information) of a DEREGISTERED device is not available, and as such the network does not have sufficient information to allow it to page the device, as such the UE is determined to be not reachable.
In the REGISTERED state, the UE has performed a successful registration with the network. The network has valid context information for the UE including valid location or routing information. This location information need not be exact but instead can simply identify the last cell or cells that the UE was known to be in. This allows the network to generate a page that will reach the UE. The UE is typically required update the network by performing a Tracking Area Update procedure, either periodically or when moving into a new tracking area (such as a new cell). This allows the network to have current location context for the UE, and allows the UE to be reachable.
From a REGISTERED state, the UE enters CONNECTED state when there is traffic between the UE and the network. In a CONNECTED state, the network does not need to page the UE as there is an active connection. The UE remains in an IDLE state when no signaling between UE and network exists. An IDLE mode UE can be reachable by a paging procedure. As will be appreciated, both IDLE and CONNECTED devices are viewed as REGISTERED, and both consume resources in the network, although the resources that they consume may be different.
As the number of the machine type devices increases it is important to provide a mechanism to help to alleviate network overloading. To facilitate this, it is envisioned that a network operator may benefit from the ability to force an MTC device to remain effectively off-line when not communicating. Conventionally this means that the device would have to be DEREGISTERED, which would prevent to device from being reachable, and may result in increased traffic when a plurality of such devices all register at the same time. One skilled in the art will appreciate that DEREGISTERING a device to conserve resources is a generally undesirable result as the device is then no longer reachable.
There exist many prior art references, such as PCT Publication No. WO 2011/002819 A1 entitled “Device, method and Apparatus for Offline Discontinuous Reception (DRX) Processing in Cellular Systems” that relate to how a mobile device can enter a power saving state and still receive network signaling, but there is a dearth of teachings on how the network can reduce the resources allocated to such a device.
Therefore, it would be desirable to provide a system and method that obviate or mitigate the above described problems